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Open Access Low-Dose Rapamycin Unmasks the Protective Potential of Targeting Intragraft NF-κB for Islet Transplants

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Islet grafts can contribute to their own destruction via the elaboration of proinflammatory genes, many of which are transcriptionally regulated by nuclear factor κ-light-chain-enhancer of activated B-cells (NF-κB). Thus, NF-κB constitutes an enticing gene therapy candidate to improve the success of islet transplantation. To test this hypothesis in vivo, we blocked NF-κB in BALB/c (H2d) to C57/BL6 (H2b) mouse islet allografts by genetically engineering islets to express the NF-κB superrepressor, IκBα. Here we show by microarray and RTqPCR that islets exhibit an intrinsic early immediate proinflammatory response, with the most highly upregulated proinflammatory genes comprising the chemokines Cxcl1, Cxcl2, Cxcl10, and Ccl2; the cytokines Tnf-α and Il-6; and the adhesion molecule Icam1. Overexpression of IκBα inhibited the expression of these genes by 50‐95% in islets and MIN6 β-cells in vitro, by inhibiting NF-κB-dependent gene transcription. Histological and RTqPCR analysis at postoperative day (POD) 10 revealed that IκBα-transduced islet allografts exhibited improved islet architecture and strong insulin-labeling with decreased Ccl2 and Il-6 mRNA levels compared to the GFP-transduced control grafts. Despite these protective effects, NF-κB-blocked islet allografts were promptly rejected in our MHC-mismatched mouse model. However, IκBα-expressing grafts did harbor localized “pockets” of Foxp3+ mononuclear cells not evident in the control grafts. This result suggested that the effect of the NF-κB blockade might synergize with regulatory T-cell-sparing rapamycin. Indeed, combining intragraft IκBα expression with low-dose rapamycin increased the mean survival time of islet allografts from 20 to 81 days, with 20% of the grafts surviving for greater than 100 days. In conclusion, rapamycin unmasks the protective potential of intragraft NF-κB blockade, which can, in some cases, permit permanent allograft survival without continuous systemic immunosuppression.
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Keywords: Inflammation; Inhibitor of κB protein (IκBα); Islet transplantation; Nuclear factor κ-light-chain-enhancer of activated B-cells (NF-κB); Rapamycin

Document Type: Research Article

Publication date: 23 December 2013

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  • Cell Transplantation publishes original, peer-reviewed research and review articles on the subject of cell transplantation and its application to human diseases. To ensure high-quality contributions from all areas of transplantation, separate section editors and editorial boards have been established. Articles deal with a wide range of topics including physiological, medical, preclinical, tissue engineering, and device-oriented aspects of transplantation of nervous system, endocrine, growth factor-secreting, bone marrow, epithelial, endothelial, and genetically engineered cells, among others. Basic clinical studies and immunological research papers are also featured. To provide complete coverage of this revolutionary field, Cell Transplantation will report on relevant technological advances, and ethical and regulatory considerations of cell transplants. Cell Transplantation is now an Open Access journal starting with volume 18 in 2009, and therefore there will be an inexpensive publication charge, which is dependent on the number of pages, in addition to the charge for color figures. This will allow work to be disseminated to a wider audience and also entitle the corresponding author to a free PDF, as well as prepublication of an unedited version of the manuscript.

    Cell Transplantation is now being published by SAGE. Please visit their website for the most recent issues.

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